This invention relates to a control apparatus for a commutatorless synchronous machine, particularly to the control circuit which controls current fed to an armature winding of the commutatorless synchronous machine.
In a conventional synchronous machine, when it operates at the relatively high speed, the actual current flowing through the armature winding is retarted in phase with respect to a nominal armature current because of, for example, the delay in the response of the control circuit. The phase-delay of the armature current results in the lowering of the power factor of the synchronous machine.
In a Japanese patent laying-open No. 50-77814 which was opened to public on June 25, 1975, the control circuit is disclosed in which the delay of the armature current is compensated by advancing the nominal pattern signal in accordance with the operating speed of the synchronous machine. Since, however, the delay of the armature current is caused not only by the delay of response of the control circuit, but also by the field current, the amount of the advanced phase in the nominal pattern signal can not be determined by only the operating speed of the synchronous machine. The synchronous machine having the control circuit as above-described, therefore, has a drawback that it is not able to operate at the preset power factor accurately.